On the Colour of Leaves of Plants and their Autumnal Changes

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                                through. When the leaf is of a light green and still more 
when it is of a yellowish colour, the nature of this ring becomes 
apparent to the naked eye, as it is then seen to exhibit a 
more or less pink or reddish <s>tune <\s> hue.
It has already been stated, that the red leaves of certain 
geraniums are rarely red all over, but in part only, the change 
of colour beginning mostly at the edges of the leaves where 
thinnest and most permeable to light and air; the 
redness advances gradually and ultimately extends over a great 
part of the surface, the remainder of the leaf being usually of 
a paler green than the rest of the leaves, or even of a yellow colour.
This change of colour from green to red is doubtless generally effected 
at the expense of the green colour, which in some cases is entirely 
replaced by the red; in others, part of the green remains un=
destroyed, but is often more or less concealed by the coating of 
red. The gradual extension of the red colour into the cells occupied 
by the chlorophyll may often be seen under a low object glass 
in thin vertical sections of the leaf; there seems to be a decom=
position of the green colour, which first becomes olive green,
yellow and then red, indeed cells are sometimes seen in which 
one side is occupied with yellow and the other, with red colouring 
matter.
The red colouring matter of plants is soluble in water and still 
more so in spirit, but owing to the difficult permeability of the 
epidermis, the colour is but slowly extracted, so that it is necessary 
as in the case of chlorophyll, to cut the leaves into small pieces.
When the red colour extends through the whole thickness of 
                            
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Manuscript details

Author
Arthur Hill Hassall
Reference
AP/69/1
Series
AP
Date
1892
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On the Colour of Leaves of Plants and their Autumnal Changes, 1892. From The Royal Society, AP/69/1

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